Turner Whitted

Measuring the perception of visual realism in images

One of the main goals in realistic rendering is to generate images that are indistinguishable from photographs – but how do observers decide whether an image is photographic or computer-generated? If this perceptual process were understood, then rendering algorithms could be developed to directly target these cues. In this paper we introduce an experimental method for measuring the perception of visual realism in images, and present the results of a series of controlled human subject experiments. These experiments cover the following visual factors: shadow softness, surface smoothness, number of light sources, number of objects, and variety of object shapes. This technique can be used to either affirm or cast into doubt common assumptions about realistic rendering. The experiments can be performed using either photographs or computergenerated images. This work provides a first step towards objectively understanding why some images are perceived as photographs, while others as computer graphics.

20.4: Displaced Filtering for Patterned Displays

This paper describes the filtering used in Microsoft ClearType. ClearType is a software system than enhances the resolution and readability of fonts on displays that contain a repeating pattern of addressable colored sub-pixels. The filtering in ClearType is based on a perceptual model of human vision. The perceptual model leads to an optimization technique for finding the best output values. The results of the optimization can be approximated by pre-filtering each color channel of an input image and then sampling each filtered color image at the spatial locations of the same colored sub-pixels in the display. We refer to this filtering followed by displaced sampling as RGB decimation. RGB decimation eliminates the phase error caused by standard anti-aliasing. A further approximation of the optimal filter yields RGB decimation with displaced box filters. Fourier analysis demonstrates that both the optimization technique and the displaced box filter suppress frequencies that contribute most to color fringing in unfiltered displaced sampling.

Fully procedural graphics

The growing application of user-defined programs within graphics processing units (GPUs) has transformed the fixed-function display pipeline into a largely programmable pipeline. In this paper we propose that the elements fed through the pipeline be made entirely procedural. To enable this, we present a modification of the conventional graphics processor in which all procedures are executed in a common processor array and the rasterizer is augmented with a more general sampling controller. By executing both the geometric and shading elements of a procedural graphics model in a single processor we retain the data amplification that distinguishes procedural descriptions without a corresponding explosion of external bandwidth.

Embedded function composition

A low-level graphics processor is assembled from a collection of hardwired functions of screen coordinates embedded directly in the display. Configuration of these functions is controlled by a buffer containing parameters delivered to the processor on-the-fly during display scan. The processor is modular and scalable in keeping with the demands of large, high resolution displays.

Overview of IBR: software and hardware issues

Image-based rendering is perceived as a new technique, as yet unsupported by hardware. In fact, IBR has been an integral part of computer graphics for some time. However it is not as well supported as one might wish in conventional graphics hardware and software libraries. This overview highlights some of the hardware and software issues of IBR, surveys current practice, and proposes guidelines for designing a unified IBR platform.

Snow crashing the diamond age: mobile devices meet sensor networks

Personal mobile computing devices share many of the same properties of nodes in a sensor network. They are both sensor-rich, power-limited, and wirelessly connected. Indeed, a number of researchers have described sensor networks composed of collections of mobile devices. Sensor networks may be naïvely characterized as instrumentation of a fixed space or structure. Mobile devices are appliances in the service of an individual. Imagining the potential of these technologies in combination is a matter of proposing applications.